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      <h1>Zodiac Decoder</h1>

      <h2>UNT Symbolic Processing</h2>
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        The Zodiac was a notorious serial murderer from the greater
        San Francisco area during the 60's and 70's. The Zodiac was
        confirmed to have seven victims with five murders, and
        claimed to have killed dozens more. He is mainly remembered
        for threatening to blowup school buses full of children. He
        skillfully manipulated the media by taunting the police
        with letters and ciphers. This is our area of interest.
        <br />
        <br />
        On July 31, 1969, less than a month after the Zodiac's
        attack on Mike Mageau and third confirmed murder of Darlene
        Ferrin, the Zodiac submitted his first cipher. It was sent
        to the Vallejo Times Herald, the San Francisco Chronicle,
        and the San Francisco Examiner in three equal parts with no
        obvious distinction as to what order they were to be read.
        Along with each part of the cipher were near identical
        hand-written letters threatening to kill a dozen people in
        a week-end rampage (if his demands of front page
        publication were not met). Each portion of the cipher was
        eventually published, though not all initially on the front
        pages and not all on the requested date.
        <br />
        <br />
        The combined cipher was 17 characters across, and 24
        characters long for a total of 408 characters. Although
        code breakers from the FBI, NSA, CIA, and Naval
        Intelligence all tried to solve the cipher, it was Donald
        and Bettye Harden, a forty-one year old high school history
        teacher and his wife, who finally cracked it. In addition
        to some prior knowledge of some basic code breaking
        techniques, Harden was able to solve the cipher by making a
        very insightful and very lucky assumption that the coded
        message began with the phrase "I like killing." Harden also
        made a number of other basic assumptions as well. Namely
        that it was a homophonic cipher (one letter being
        potentially represented by many symbols) and that the
        message read from left to right and top to bottom.
        <br />
        <br />
        The Zodiac's second cipher arrived on November 8th, 1969 at
        the San Francisco Chronicle. The cipher was received less
        than one month after the Zodiac's fifth and last confirmed
        murder, cab driver Paul Stine. Contained in the envelope
        with the cipher were a greeting card and a bloody piece of
        Paul Stine's shirt taken from the scene of his murder. This
        second cipher was 340 characters all together (68
        characters less than the previous cipher). In addition this
        new 340 cipher had 63 unique symbols, more than the
        previous. The combination of more unique symbols and a
        shorter message gave this cipher a much higher degree of
        complexity.
        <br />
        <br />
        Although the Zodiac sent three more ciphers to the news
        papers, the third and forth are very short and therefore no
        conclusive analysis can be done on them. Author Robert
        Graysmith, claimed to have solved the 340 cipher. However,
        it is our belief that even though it is the best to date,
        it is not a complete nor satisfactory solution. As so many
        other dedicated cipher-crackers, we pick up where other
        gave up...
        <br />
        <br />
        The Zodiac was never caught.
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      <p>© 2007 University of North Texas</p>

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